Methods for generating a unified virtual snapshot and systems thereof

ABSTRACT

A method, computer readable medium, and system for generating a unified virtual snapshot in accordance with embodiments of the present invention includes invoking with a file virtualization system a capture of a plurality of physical snapshots. Each of the physical snapshots comprises content at a given point in time in one of the plurality of data storage systems. A unified virtual snapshot is generated with the file virtualization system based on the captured plurality of the physical snapshots.

This application is a continuation of prior U.S. patent application Ser. No. 12/334,281, filed Dec. 12, 2008, and claims the benefit of U.S. Provisional Patent Application Ser. No. 61/013,539, filed Dec. 13, 2007, and this application is also related to U.S. patent application Ser. No. 12/334,294, filed Dec. 12, 2008, now abandoned, each of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates generally to methods and systems for capturing snapshots of file systems and, more particularly, to methods for generating a unified virtual snapshot from a plurality of physical snapshots of a heterogeneous network storage system and systems thereof.

BACKGROUND

Often files and associated data in computer systems are remotely stored on one or more network storage devices. In anticipation of a possible restore request from a user computer system coupled to a network storage device, a physical snapshot of the content in the network storage device may be captured at a recorded time. If the user computer system has a need for and requests a restore, the captured physical snapshot can be used to recover contents from the network storage device as of the recorded time.

File virtualization systems provide methods for managing and presenting a plurality of network storage devices as a single, unified file system. Basically, file virtualization decouples the presentation of a file system from its' physical composition. Unfortunately, when file virtualization is implemented, there is no method or system for generating and providing a unified virtual snapshot in a heterogeneous storage network system.

SUMMARY

A method for generating a unified virtual snapshot in accordance with embodiments of the present invention includes invoking with a file virtualization system a capture of a plurality of physical snapshots. Each of the physical snapshots comprises content at a given point in time in one of the plurality of data storage systems. A unified virtual snapshot is generated with the file virtualization system based on the captured plurality of the physical snapshots.

A computer readable medium having stored thereon instructions for methods for generating a unified virtual snapshot in accordance with other embodiments of the present invention comprising machine executable code which when executed by at least one processor, causes the processor to perform steps including invoking with a file virtualization system a capture of a plurality of physical snapshots. Each of the physical snapshots comprises content at a given point in time in one of the plurality of data storage systems. A unified virtual snapshot is generated with the file virtualization system based on the captured plurality of the physical snapshots.

A system that generates a unified virtual snapshot in accordance with other embodiments of the present invention includes an invocation system and a virtual snapshot system in a file virtualization system. The invocation system invokes a capture of a plurality of physical snapshots. Each of the physical snapshots comprises content in one of the plurality of data storage systems at a given point in time. The virtual snapshot system generates a unified virtual snapshot based on the captured plurality of the physical snapshots.

The present invention provides a number of advantages including providing a unified virtual snapshot from a plurality of physical snapshots of contents of file systems distributed across several independent, network storage devices. Additionally, the present invention provides a method and system which enables the use of snapshots in environments that implement file virtualization. Further, the present invention captures and generates snapshots which can be utilized to re-assemble contents of file systems with or without the file virtualization system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example of a system that generates and uses a virtual snapshot from a plurality of physical snapshots of a heterogeneous network storage system;

FIG. 2A is a functional block diagram of an example of a method for processing requests with file virtualization;

FIG. 2B is a flow chart of the example of the method for processing requests with file virtualization illustrated in FIG. 2A;

FIG. 3A is a functional block diagram of an example of a method for generating one or more unified virtual snapshots;

FIG. 3B is a flow chart of the example of the method for generating one or more unified virtual snapshots illustrated in FIG. 3A;

FIG. 4A is a functional block diagram of a method for processing requests with file virtualization after the creation of one or more unified virtual snapshots;

FIG. 4B is a flow chart of the example of the method for processing requests with file virtualization after the creation of one or more unified virtual snapshots illustrated in FIG. 4A;

FIG. 5A is a functional block diagram of the hierarchy of unified virtual snapshots and physical snapshots;

FIG. 5B is a flow chart of the example of the method for recovering content in a heterogeneous storage system;

FIG. 6 is a diagram of an example of a virtual snapshot configuration record; and

FIG. 7 is a diagram of an example of a snapshot command on a network storage device.

DETAILED DESCRIPTION

An example of a system 10 that generates and uses a virtual snapshot of a heterogeneous network storage system is illustrated in FIG. 1, although the present invention can be utilized in homogeneous network storage systems with one or more storage devices. This system 10 includes a client system 12, a file virtualization system 14, data storage systems 16(1) and 16(2), and metadata storage system 18, although this system 10 can include other numbers and types of systems, devices, equipment, parts, components, and/or elements in other configurations. The present invention provides a number of advantages including providing a unified virtual snapshot from a plurality of physical snapshots of contents of file systems distributed across several independent, network storage devices.

Referring more specifically to FIG. 1, the client system 12 utilizes the file virtualization system 14 to conduct one or more operations with one or more of the data storage systems 16(1), 16(2), and 18, such as to store a file, delete a file, create a file, and restore a file by way of example only, although other numbers and types of network systems could be utilizing these resources and other types and numbers of functions could be performed. The client system 12 includes a central processing unit (CPU) or processor, a memory, user input device, a display, and an interface system, and which are coupled together by a bus or other link, although the client system 12 can include other numbers and types of components, parts, devices, systems, and elements in other configurations. The processor in the client system 12 executes a program of stored instructions as described and illustrated herein, although the processor could execute other numbers and types of programmed instructions.

The memory in the client system 12 stores these programmed instructions for one or more aspects of the present invention as described and illustrated herein, although some or all of the programmed instructions could be stored and/or executed elsewhere. A variety of different types of memory storage devices, such as a random access memory (RAM) or a read only memory (ROM) in the system or a floppy disk, hard disk, CD ROM, or other computer readable medium which is read from and/or written to by a magnetic, optical, or other reading and/or writing system that is coupled to one or more processors, can be used for the memory in the client system 12.

The user input device in the client system 12 is used to input selections, such as to store a file, delete a file, create a file, and restore a file, although the user input device could be used to input other types of data and interact with other elements. The user input device can include a computer keyboard and a computer mouse, although other types and numbers of user input devices can be used. The display in the client system 12 is used to display information, such as a file or directory, although other types and amounts of information can be displayed in other manners. The display can include a computer display screen, such as a CRT or LCD screen, although other types and numbers of displays could be used.

The interface system in the client system 12 is used to operatively couple and communicate between the client system 12 and the file virtualization system 14 via a communications network 20, although other types and numbers of communication networks or systems with other types and numbers of configurations and connections to other systems and devices can be used.

The file virtualization system 14 manages file virtualization and the generation of unified virtual snapshots, although other numbers and types of systems can be used and other numbers and types of functions can be performed. The file virtualization system 14 includes a central processing unit (CPU) or processor, a memory, and an interface system which are coupled together by a bus or other link, although other numbers and types of components, parts, devices, systems, and elements in other configurations and locations can be used. The processor in the file virtualization system 14 executes a program of stored instructions for one or more aspects of the present invention as described and illustrated by way of the embodiments herein, such as managing file virtualization and the generation of unified virtual snapshots, although the processor in file virtualization system 14 could execute other numbers and types of programmed instructions.

The memory in the file virtualization system 14 stores these programmed instructions for one or more aspects of the present invention as described and illustrated herein, although some or all of the programmed instructions could be stored and/or executed elsewhere. A variety of different types of memory storage devices, such as a random access memory (RAM) or a read only memory (ROM) in the system or a floppy disk, hard disk, CD ROM, DVD ROM, or other computer readable medium which is read from and/or written to by a magnetic, optical, or other reading and/or writing system that is coupled to one or more processors, can be used for the memory in the file virtualization system 14.

The interface system in the file virtualization system 14 is used to operatively couple and communicate between the file virtualization system 14 and the client system 12, the data storage system 16(1), the data storage system 16(2), and the metadata storage system 18 via the communications networks 20, although other types and numbers of communication networks or systems with other types and numbers of connections and configurations can be used.

Each of the data storage systems 16(1) and 16(2) is a network storage device for files, directories, and other data, although other numbers and types of storage systems which could have other numbers and types of functions and store other data could be used. In this example, data storage system 16(1) is a different type of storage device, e.g. different make and/or model, from the data storage system 16(2) to form a heterogeneous network storage system, although the present invention can work with other numbers and types of storage systems, such as a homogeneous system.

Each of the data storage systems 16(1) and 16(2) include a central processing unit (CPU) or processor, a memory, and an interface system which are coupled together by a bus or other link, although other numbers and types of components, parts, devices, systems, and elements in other configurations can be used. By way of example only, the storage systems may not have their own separate processing capabilities. In this example, the specialized processor in each of the data storage systems 16(1) and 16(2) executes a program of stored instructions for one or more aspects of the present invention as described and illustrated by way of the embodiments herein, such as to capture a physical snapshot by way of example only, although the processor in each of the data storage system could execute other numbers and types of programmed instructions.

The memory in each of the data storage systems 16(1) and 16(2) store these programmed instructions for one or more aspects of the present invention as described and illustrated herein, although some or all of the programmed instructions could be stored and/or executed elsewhere. A variety of different types of memory storage devices, such as a random access memory (RAM) or a read only memory (ROM) in the system or a floppy disk, hard disk, CD ROM, DVD ROM, or other computer readable medium which is read from and/or written to by a magnetic, optical, or other reading and/or writing system that is coupled to one or more processors, can be used for the memory in each of the data storage systems 16(1) and 16(2).

The interface system in the data storage system 16(1) and the interface in the data storage system 16(2) are each used to operatively couple and communicate between the data storage system 16(1) and the file virtualization system 14 and between the data storage system 16(2) and the file virtualization system 14 via communication network 20, although other types and numbers of communication networks or systems with other types and numbers of configurations and connections to other systems and devices can be used.

The metadata storage system 18 is another type of network storage device to store and manage global file virtualization metadata from data storage systems 16(1) and 16(2), although other numbers and types of storage systems which could have other numbers and types of functions, which is connected in other manners, and which could store other types of data and information could be used. In this particular example, the metadata storage system 18 is external to the file virtualization system 14, although the metadata storage 18 could be located in the file virtualization system 14. The metadata storage system 18 includes a central processing unit (CPU) or processor, a memory, and an interface system which are coupled together by a bus or other link, although other numbers and types of components, parts, devices, systems, and elements in other configurations can be used for the storage system. By way of example only, the storage system may not have its own separate processing capabilities. In this example, the specialized processor in the metadata storage system 18 executes a program of stored instructions for one or more aspects of the present invention as described and illustrated by way of the embodiments herein, although the processor in metadata storage system 18 could execute other numbers and types of programmed instructions.

The memory in the metadata storage system 18 stores these programmed instructions for one or more aspects of the present invention as described and illustrated herein, although some or all of the programmed instructions could be stored and/or executed elsewhere. A variety of different types of memory storage devices, such as a random access memory (RAM) or a read only memory (ROM) in the system or a floppy disk, hard disk, CD ROM, DVD ROM, or other computer readable medium which is read from and/or written to by a magnetic, optical, or other reading and/or writing system that is coupled to the processor in the metadata storage system 18.

The interface system in the metadata storage system 18 is used to operatively couple and communicate between the metadata storage system 18 and the file virtualization system 14 via the communications network 20, although other types and numbers of communication networks or systems with other types and numbers of configurations and connections to other systems and devices can be used.

Although embodiments of the client system 12, the file virtualization system 14, the data storage systems 16(1) and 16(2), and the metadata storage system 18 are described herein, each of these systems can be implemented on any suitable computer system or computing device. It is to be understood that the devices and systems of the embodiments described herein are for exemplary purposes, as many variations of the specific hardware and software used to implement the embodiments are possible, as will be appreciated by those skilled in the relevant art(s).

Furthermore, each of the systems of the embodiments may be conveniently implemented using one or more general purpose computer systems, microprocessors, digital signal processors, and micro-controllers, programmed according to the teachings of the embodiments, as described and illustrated herein, and as will be appreciated by those ordinary skill in the art.

In addition, two or more computing systems or devices can be substituted for any one of the systems in any embodiment of the embodiments. Accordingly, principles and advantages of distributed processing, such as redundancy and replication also can be implemented, as desired, to increase the robustness and performance of the devices and systems of the embodiments. The embodiments may also be implemented on computer system or systems that extend across any suitable network using any suitable interface mechanisms and communications technologies, including by way of example only telecommunications in any suitable form (e.g., voice and modem), wireless communications media, wireless communications networks, cellular communications networks, G3 communications networks, Public Switched Telephone Network (PSTNs), Packet Data Networks (PDNs), the Internet, intranets, and combinations thereof.

The embodiments may also be embodied as a computer readable medium having instructions stored thereon for one or more aspects of the present invention as described and illustrated by way of the embodiments herein, as described herein, which when executed by a processor, cause the processor to carry out the steps necessary to implement the methods of the embodiments, as described and illustrated herein.

An overview of the present invention is set forth below. With this example of the present invention, a file virtualization layer (FV1) provided by file virtualization system 14 exists between the application in client system 12 or CL1 and the data storage systems 16(1) and 16(2) (also referred to as DS1 and DS2), although other numbers and types of client systems and storage systems could be used. This file virtualization layer provided by file virtualization system 14 manages metadata in data storage 18 that tracks the location of files and directories that are distributed across data storage systems 16(1) and 16(2) in this particular example.

To generate or create a unified virtual snapshot, file virtualization system 14 erects an I/O barrier to substantially suspend data storage communications between client system 12 and data storage systems 16(1) and 16(2) and metadata storage system 18. This suspension permits either an administrator or application at client system 12 or file virtualization system 14 to request or invoke a capture of physical snapshots of content on data storage systems 16(1) and 16(2) and metadata storage system 18 using an application programming interface (API) or command line interface (CLI), although other manners for invoking a capture of physical snapshots, such as a periodic automated invocation could be used. Once all of the physical snapshots have been captured or otherwise completed by file virtualization system 14, the unified virtual snapshot is generated by file virtualization system 14 and the I/O barrier is removed to allow storage data communications to resume. The unified virtual snapshot comprises the captured physical snapshots which are mapped together by file virtualization system 14 to form the virtual snapshot.

In this example, the I/O barrier is implemented by the file virtualization system 14 at the application protocol level, such as NFS or CIFS by way of example, although the I/O barrier could be implemented in other manners. Packets are accepted at a transport level, such as UDP or TCP by way of example, but are not proxied by file virtualization system 14 to the data storage systems 16(1) and 16(2) and traffic to the metadata storage system 18 is halted while the I/O barrier is asserted. As implemented, the barrier operation is substantially transparent to the operator at the client system 12 and at most the file system seems momentarily slow, although system can be arranged in other manners, such as to provide notice of the implementation of the barrier if desired.

To create a persistent record of the location of files and directories in physical snapshots, once the I/O barrier is asserted and before a physical snapshot occurs the file virtualization system 14 initiates copying or writing of a virtual snapshot configuration record into data storage systems 16(1) and 16(2) and metadata storage system 18. The virtual snapshot configuration record is a unique record written in each of the data storage systems 16(1) and 16(2) and metadata storage system 18 that allows an operator or program to locate components, e.g. a file of a virtual snapshot, although other types and amounts of information could be included. More specifically, the snapshot configuration record records the members of a unified virtual snapshot, i.e. in this particular example the members are data storage systems 16(1) and 16(2) and metadata storage system 18, although the snapshot configuration record can store other types and amounts of data. By way of example only, a virtual snapshot configuration record is illustrated in FIG. 6. In this example, the virtual snapshot configuration records are made unique by a field in the header of each record, although other manners for providing a unique identifier can be used.

The virtual snapshot configuration record is included in the physical snapshots to aid in recovery. With the snapshot configuration record and the stored metadata on the file virtualization system 14, the file virtualization system 14 can locate a particular file or directory. Additionally, by including the virtual snapshot configuration record in the physical snapshot, an external application that knows the format of the stored metadata can use that metadata and the snapshot configuration record to locate a file without file virtualization.

Once a unique virtual snapshot configuration record is copied to each data storage systems 16(1) and 16(2) and metadata storage system 18, the data storage systems 16(1) and 16(2) and metadata storage system 18 are invoked by file virtualization system 14 to capture physical snapshots which will contain this virtual snapshot configuration record, although the data storage systems 16(1) and 16(2) and metadata storage system 18 can be invoked to capture physical snapshots by other systems in other manners. The data storage systems 16(1) and 16(2) and metadata storage system 18 take a physical snapshot in response to this invocation.

By way of example only, a snapshot command which can be used by data storage systems 16(1) and 16(2) and metadata storage system 18 is illustrated in FIG. 7, although other types of commands could be used. Again, this method effectively embeds the unique virtual snapshot configuration record into each of the physical snapshots themselves.

Generation of unified virtual snapshots is implemented by the file virtualization layer in file virtualization system 14, although the generation can be implemented by other systems. Virtual directories are dynamically created that contain a list of available virtual snapshots at different points in time in file virtualization system 14. Each virtual snapshot subdirectory contains files and directories that exist in the physical snapshots of the contents of the file systems on data storage systems 16(1) and 16(2) and metadata storage system 18 in this example.

Referring now to FIGS. 2A and 2B, an example of a method for processing requests with a file virtualization is described below. In step 22, client system 12 (also known as CL1) issues a request CL-REQ-1-1 for a file creation operation of a file ‘a’ to file virtualization system 14 (also known as FV1), although other types and numbers of requests could be issued from other types and numbers of systems.

In step 24, file virtualization system 14 receives the request CL-REQ-1-1 from client system 12. Using the stored metadata, the file virtualization system 14 translates the request CL-REQ-1-1 into a file virtualization request FV-REQ-1-1 which is suitable for execution on data storage system 16(1) (also known as DS1) in which the file is actually located, although other types of requests for other systems could be received.

In step 26, data storage system 16(1) receives the request FV-REQ-1-1 from the file virtualization system 14. In response to the received request FV-REQ-1-1 the data storage system 16(1) performs the creation of file ‘a’ and issues reply DS-RSP-1-1 back to file virtualization system 14, although the data storage system 16(1) could perform other types and numbers of operations based on the received request.

In step 28, file virtualization system 14 receives the reply DS-RSP-1-1 from the data storage system 16(1). In response to the reply DS-RSP-1-1, the file virtualization system 14 generates metadata about the file creation operation and transmits a FV-REQ-1-2 request to metadata storage system 18 (also known as MD1) to record this generated metadata.

In step 30, metadata storage system 18 receives the FV-REQ-1-2 request and stores the generated metadata. Once the FV-REQ-1-2 request is processed, the metadata storage system 18 issues a reply MD-RSP-1-1 to the file virtualization system 14.

In step 32, file virtualization system 14 receives the reply MD-RSP-1-1 from the metadata storage system 18. Next, the file virtualization system 14 using information gathered from the reply MD-RSP-1-1 and the reply DS-RSP-1-1 generates a file virtualization reply FV-RSP-1-1 and issues the reply FV-RSP-1-1 back to client system 12. The file virtualization system 14 also updates the stored file virtualization configuration record to reflect this completed operation.

Referring now to FIGS. 3A and 3B, an example of a method for generating one or more unified virtual snapshots is described below. In step 50, client system 12 issues request CL-REQ-2-1 for a file deletion operation of file ‘a’ to file virtualization system 14, although other types and numbers of requests could be issued from other types and numbers of systems.

In step 52, file virtualization system 14 accepts the request CL-REQ-2-1 from the client system 12, although other types and numbers of requests could be received. Since at this time an I/O barrier is asserted, the file virtualization system 14 performs no action at this time on the request CL-REQ-2-1 from the client system 12, although once the I/O barrier is removed the file virtualization system 14 will process the request.

In step 54, while the I/O barrier is asserted, the file virtualization system 14 generates and transmits a write request WRITE_REQ_2_* to each of the data storage systems 16(1) and 16(2) and the metadata storage system 18 to write the virtualization snapshot configuration record persistent storage, although other types and numbers of requests can be transmitted to other types and numbers of systems. More specifically, in this particular example the file virtualization system 14 generates and transmits a write request WRITE_REQ_2_1 to data storage system 16(1), a write request WRITE_REQ_2_2 to data storage system 16(2), and a WRITE_REQ_2_3 to metadata storage system 18 to each write the virtualization snapshot configuration record in persistent storage.

Once the virtualization snapshot configuration record is written in persistent storage, each of the data storage systems 16(1) and 16(2) and the metadata storage system 18 generates and transmits a response WRITE_RSP_2_* to the file virtualization system 14, although other types and numbers of responses can be transmitted to other types and numbers of systems. More specifically, in this particular example data storage system 16(1) generates and transmits a WRITE_RSP_2_1, the data storage system 16(2) generates and transmits a WRITE_RSP_2_2, and the metadata storage system 18 generates and transmits a WRITE_RSP_2_3 to the file virtualization system 12 once the virtualization snapshot configuration record is written in persistent storage in each storage system.

In step 56, file virtualization system 14 optionally flushes metadata changes, write ahead logs, and any other information required to ensure consistency with the file virtualization metadata snapshot, although the file virtualization system 14 may perform other types and numbers of operations.

In step 58 once the optional flush operations described above in step 56 are completed, the file virtualization system 14 invokes the execution of snapshot operations on data storage systems 16(1) and 16(2) and metadata storage system 18 by generating and transmitting snapshot requests SNAP_REQ_2_*, although the snapshot operations can be invoked in other manners and physical snapshots can be taken in other types and numbers of systems. More specifically, in this particular example file virtualization system 14 generates and transmits request SNAP_REQ_2_1 to data storage systems 16(1) to take a physical snapshot, request SNAP_REQ_2_2 to data storage systems 16(2) to take a physical snapshot, and request SNAP_REQ_2_3 to data storage systems 18 to take a physical snapshot.

In step 60, the data storage systems 16(1) and 16(2) and the metadata storage system 18 each receive and process the requests SNAP_REQ_2_1, SNAP_REQ_2_3, and SNAP_REQ_2_3, respectively, to perform a physical snapshot operation to capture a physical snapshot in each of the data storage systems 16(1) and 16(2) and the metadata storage system 18.

Once the physical snapshots have been taken, the data storage systems 16(1) and 16(2) and the metadata storage system 18 each generate and transmit a response SNAP-RSP-2-* when each of the physical snapshots at the data storage systems 16(1) and 16(2) and the metadata storage system 18 have been taken, although other types and numbers of responses can be transmitted to other types and numbers of systems. More specifically, in this particular example data storage system 16(1) generates and transmits a SNAP-RSP-2-1, the data storage system 16(2) generates and transmits a SNAP-RSP-2-2, and the metadata storage system 18 generates and transmits a SNAP-RSP-2-3 to the file virtualization system 12 when each of the physical snapshots at the data storage systems 16(1) and 16(2) and the metadata storage system 18 have been taken.

In step 62, file virtualization system 14 receives completion notifications from data storage systems 16(1) and 16(2) and metadata storage system 18 indicating that the physical snapshots are completed, i.e. the data and metadata are consistent as of the point of time the I/O barrier has been asserted, and then records completion of the unified virtual snapshot. Once all of the responses SNAP-RSP-2-* have been received, the file virtualization system 14, lowers the asserted I/O barrier and processes request CL-REQ-2-1 as well as any other requests.

Referring to FIGS. 4A and 4B, an example of a method for processing requests with a file virtualization after the creation of one or more unified virtual snapshots is described below. In step 70, client system 12 issues request CL-REQ-3-1 for a file deletion operation of file ‘a’ to file virtualization system 14, although other types and numbers of requests could be issued from other types and numbers of systems.

In step 72, file virtualization system 14 receives the request CL-REQ-3-1 from client system 12. Using the stored metadata, the file virtualization system 14 translates the request CL-REQ-3-1 into a file virtualization request FV-REQ-3-1 which is suitable for execution on data storage system 16(1) in which the file is actually located, although other types of requests for other systems could be received.

In step 74, data storage system 16(1) receives the request FV-REQ-3-1 request from the file virtualization system 14. In response to the received request FV-REQ-3-1, the data storage system 16(1) performs the deletion of file ‘a’ and issues reply DS-RSP-3-1 back to file virtualization system 14, although the data storage system 16(1) could perform other types and numbers of operations based on the received request. Although deleted by this operation, file ‘a’ remains in the unified virtual snapshot generated as described with reference to FIGS. 3A and 3B.

In step 76, file virtualization system 14 receives the reply DS-RSP-3-1 from the data storage system 16(1). In response to the reply DS-RSP-3-1, the file virtualization system 14 generates metadata about the file deletion operation and transmits a FV-REQ-3-2 request to metadata storage system 18 to record this generated metadata

In step 78, metadata storage system 18 receives the request FV-REQ-3-2 and updates the metadata stored on metadata storage system 18 to reflect the deletion of file ‘a’, although other types and numbers of updates could be recorded. Once the FV-REQ-3-2 request is processed, the metadata storage system 18 issues a reply MD-RSP-3-1 to the file virtualization system 14.

In step 80, file virtualization system 14 receives the reply MD-RSP-3-1 from the metadata storage system 18. Next, the file virtualization system 14 using information gathered from the reply MD-RSP-3-1 and the reply DS-RSP-3-1 generates and issues a file virtualization reply FV-RSP-3-1 back to client system 12.

An example of the hierarchy of unified virtual snapshots and physical snapshots is illustrated in the functional block diagram in FIG. 5A and is described below. As set forth in functional block 90, each virtual directory contains a virtual snapshot listing directory (VSLD). As set forth in functional block 92, each VSLD contains a list of virtual snapshots (VSN). As set forth in functional block 94, each VSN is an aggregation of physical snapshots (PSNs). As set forth in functional block 96, each Physical directory contains a physical snapshot listing directory (PSLD). As set forth in functional block 98, each PSLD contains a list of physical snapshots (PSN). As set forth in functional block 100, each PSN is a “point in time” image of the file system, such as of data storage system 16(1), data storage system 16(2), or metadata storage system 18, by way of example only.

An example of a method for recovering content in a heterogeneous storage system is illustrated in FIG. 5B and is described below. In step 120, the client system 12 generates and issues a request CL-REQ-2-1 to file virtualization system 14 to access a file in the unified virtual snapshot, although other types and numbers of requests could be issued.

In step 122, the file virtualization system 14 receives the request CL-REQ-2-1 from client system 12, although other types and numbers of requests could be received. The file virtualization system 14 processes the request CL-REQ-2-1 which includes a marker indicating a traversal of a virtual snapshot listing directory, although in response to the request the file virtualization system 14 could have other types and numbers of indicators. By way of example only, the request could have a marker which indicated a search of the virtual snapshot listing directory was needed to identify the virtual snapshot or the absence of a marker could indicate the need for a search. If a search is indicated by processing the request CL-REQ-2-1, the file virtualization system 14 identifies the virtual snapshot in the virtual snapshot listing based on one or more factors, such as a particular date range in the request, although other manners for identifying the virtual snapshot can be used.

In step 124, the file virtualization system 14 associates request CL-REQ-2-1 with the identified virtual snapshot VSN-1 based on data in the processed request CL-REQ-2-1, such as a specific identification of the virtual snapshot VSN-1, although other manners for identifying the virtual snapshot can be used.

In step 126, based on data in the request CL-REQ-2-1, the file virtualization system 14 determines which of two methods for associating the request CL-REQ-2-1 with one of the captured physical snapshots of data storage system 16(1), data storage system 16(2), and metadata storage system 18 to use, although the file virtualization system 14 could determine which method to use in other manners and could select from other types and numbers of methods In this particular example, one of these methods searches virtualization metadata (cached or persistent) to map the request to a captured physical snapshot and the other method searches the captured physical snapshot for each of the storage systems for the target of the request.

If in step 126 the file virtualization system 14 determines that the method which searches virtualization metadata should be used, then the file virtualization system 14 proceeds to step 128. In step 128, the file virtualization system 14 searches stored virtualization metadata (cached or persistent) to map the target identified in the request CL-REQ-2-1 to one of the captured physical snapshots of one of data storage system 16(1), data storage system 16(2), and metadata storage system 18. Based on the search, the file virtualization system 14 identifies one of these captured physical snapshots, although the file virtualization system can perform other operations based on the result of this search, such as generating and transmitting a message to client system 12 that the request CL-REQ-2-1 can not be completed.

If in step 126 the file virtualization system 14 determines that the method which searches the captured physical snapshots should be used, then the file virtualization system 14 proceeds to step 130. In step 130, the file virtualization system 14 searches the captured physical snapshots for each of the data storage systems 16(1) and 16(2) and metadata storage system 18 for a target identified in the request CL-REQ-2-1. Based on the search, the file virtualization system 14 either identifies one of these captured physical snapshots, although the file virtualization system 14 can perform other operations based on the result of this search, such as generating and transmitting a message to client system 12 that the request CL-REQ-2-1 can not be completed.

In step 132, once the captured physical snapshot has been identified, the file virtualization system 14 translates the request CL-REQ-2-1 in a format suitable for execution on the data storage system 16(1) or data storage system 16(2) from which the identified captured physical snapshot was taken. Once the request CL-REQ-2-1 has been translated, the file virtualization system 14 forwards the translated request CL-REQ-2-1 to the data storage system 16(1) or the data storage system 16(2) from which the identified captured physical snapshot was taken. The data storage system 16(1) or data storage system 16(2) from which the identified captured physical snapshot was taken processes the translated request CL-REQ-2-1, executes any operations, and generates and transmits a response back to the file virtualization system 14, although other types and numbers of operations could be performed based on the received translated request.

In step 134, the file virtualization system 14 translates the response from the data storage system 16(1), data storage system 16(2), or metadata storage system 18 which processed the translated request CL-REQ-2-1 and issues a reply back to the client system 12, although the file virtualization system 14 could perform other types and numbers of operations based on the received response.

Accordingly, as illustrated by the description herein the present invention provides a number of advantages including providing a unified virtual snapshot from a plurality of physical snapshots of contents of file systems distributed across several independent, network storage devices of dissimilar make and model. Additionally, the present invention provides a method and system which enables the use of snapshots in environments that implement file virtualization. Further, the present invention captures and generates snapshots which can be utilized to re-assemble contents of file systems with or without the file virtualization system.

Having thus described the basic concept of the invention, it will be rather apparent to those skilled in the art that the foregoing detailed disclosure is intended to be presented by way of example only, and is not limiting. Various alterations, improvements, and modifications will occur and are intended to those skilled in the art, though not expressly stated herein. These alterations, improvements, and modifications are intended to be suggested hereby, and are within the spirit and scope of the invention. Additionally, the recited order of processing elements or sequences, or the use of numbers, letters, or other designations therefore, is not intended to limit the claimed processes to any order except as may be specified in the claims. Accordingly, the invention is limited only by the following claims and equivalents thereto. 

What is claimed is:
 1. A method for utilizing a virtual snapshot, the method comprising: associating a request relating to a file in one of a plurality of data storage systems to one of one or more physical snapshots of one of the plurality of data storage systems in a virtual snapshot; invoking an execution of the request relating to the file at the one of the plurality of data storage systems based on the associating; and providing a response based on the invoked execution of the request.
 2. The method as set forth in claim 1 further comprising searching a virtual snapshot listing directory to identify the virtual snapshot based on one or more factors.
 3. The method as set forth in claim 2 wherein the one or more factors comprise a date range for the virtual snapshot.
 4. The method as set forth in claim 1 wherein the associating is based on a search of virtualization metadata to associate the request to the one or one or more physical snapshots or a search in the one or more physical snapshots for a target identified in the request to associate the request to the one or one or more physical snapshots
 5. The method as set forth in claim 1 further comprising translating the request for the invocation of the execution of the request at the one of the plurality of data storage systems based on the associating.
 6. The method as set forth in claim 5 wherein the providing the response based on the invoked execution of the request further comprises: receiving the response from the invoked execution of the request; and translating the received response to another format suitable for a requesting system which submitted the request; and providing the translated response to the requesting system.
 7. A non-transitory computer readable medium having stored thereon instructions for utilizing a virtual snapshot comprising machine executable code which when executed by at least one processor, causes the processor to perform steps comprising: associating a request relating to a file in one of a plurality of data storage systems to one of one or more physical snapshots of one of the plurality of data storage systems in a virtual snapshot; invoking an execution of the request relating to the file at the one of the plurality of data storage systems based on the associating; and providing a response based on the invoked execution of the request. 20
 8. The medium as set forth in claim 7 further comprising searching a virtual snapshot listing directory to identify the obtained virtual snapshot based on one or more factors.
 9. The medium as set forth in claim 8 wherein the one or more factors comprise a date range for the virtual snapshot.
 10. The medium as set forth in claim 7 wherein the associating is based on a search of virtualization metadata to associate the request to the one or one or more physical snapshots or a search in the one or more physical snapshots for a target identified in the request to associate the request to the one or one or more physical snapshots.
 11. The medium as set forth in claim 7 further comprising translating the request for the invocation of the execution of the request at the one of the plurality of data storage systems based on the associating.
 12. The medium as set forth in claim 11 wherein the providing the response based on the invoked execution of the request further comprises: receiving the response from the invoked execution of the request; and translating the received response to another format suitable for a requesting system which submitted the request; and providing the translated response to the requesting system.
 13. A file virtualization system, comprising: at least one of configurable hardware logic configured to be capable of implementing or a processor coupled to a memory and configured to execute programmed instructions stored in the memory comprising: associating a request relating to a file in one of a plurality of data storage systems to one of one or more physical snapshots of one of the plurality of data storage systems in a virtual snapshot; invoking an execution of the request relating to the file at the one of the plurality of data storage systems based on the associating; and providing a response based on the invoked execution of the request.
 14. The system as set forth in claim 13 wherein the identification system searches a virtual snapshot listing directory stored in one or more memory systems to identify the obtained virtual snapshot based on one or more factors.
 15. The system as set forth in claim 14 wherein the one or more factors comprise a date range for the virtual snapshot.
 16. The system as set forth in claim 13 wherein the association system associates based on a search of virtualization metadata to associate the request to the one or one or more physical snapshots or a search in the one or more physical snapshots for a target identified in the request to associate the request to the one or one or more physical snapshots.
 17. The system as set forth in claim 13 wherein the invocation system translates the request for the invocation of the execution of the request at the one of the plurality of data storage systems based on the associating.
 18. The system as set forth in claim 17 wherein the invocation system receives and translates the response to another format suitable for a requesting system which submitted the request and the communication system provides the translated response to the requesting system. 